Aluminum alloys



not more than 1% of iron or Patented Jul 18, 1939 UNITED STATES 2,106,490 summon more Isamu Igarashi and Goro Kitahara, Fuse, Japan,

assignors to Snmitomo,Kinzokn-Kogyo Kabushiki Kaisha, Osaka, Japan No Drawing.

Original application June 20, 1938,

Serial No. 214,809. Divided and. this applicatlon December 15, 1936 April 6, 1939, Serial No. 266,419. In Japan This application is a division of the applicants earlier application, Ser. No. 214,809, filed June 20, 1938. v

This invention relates to improved light alloys having high tensile strength and consisting of zinc, copper, magnesium, manganese, chromium, calcium and aluminum, and has for its object to provide light alloys devoid of season cracking. Hitherto, such: light alloys as E alloys and Sanders alloys which consist of copper, zinc, magnesium, manganese and aluminum have been known as having high tensile strength; but where sentative alloys according to the Composition, percent Tensile Elongation strength 50 mm. crack Cu Zn Mg Mu Ca Cr Al liq/mm. Percent 1.... 2. 5 20 o. 5 0, 5 l0 Appears within one day. 2---. 8 1.5 0.5 55 15 Do. 2 8 l. 5 0. 5 59 14 Do. 4---. 2 8 l. 5 1. 2 0.02 59. 0 a 15 No appearance even after one year. 5;--. 2' 8 1.5 1.5 0.04 0.25 61.0 14 Do. 6."- 2.5 10 1.5 1.5 0.05 0.25 60.0 14 D0. 2 8 1.5 0.5 0.09 0.30 do 59.8 15 Do.

the utmost strength and durability are required,

they were unsuitable for use due to their harmful property of season cracking. The present invention accordingly is to obviate the above-mentioned defect and to provide an alloy which is well adapted for use where non-season cracking is essential. I

After a long series of tests and investigation, it was discovered that the addition of 0.054% of chromium and 0.01-0.2% of calcium to the known alloys was effective in eliminating from the alloys the defect of season cracking without sacrificing their tensile strength. Moreover, these elements are capable of making the grain structure of the alloys in the cast state much finer and consequently impartforgeabili-ty thereto. 'lhese elements also have a tendency to increase the' fluidity of the molten metal in the refining process. Still furthenthe presence of silicon as impurities does not impart any inferior guality to the alloys. The present invention accordingly provides aluminum alloys containing 13% of copper, 4-2095 of zinc, 1-2% of magnesium, 0.1-2% of manganese, 0.01-0.5% of chromium, 0.01-0.2% of calcium, and less than 1% of iron and silicon as immirities.

Test pieces which had been properly quenched and tempered were subjected to tensile tests and the season cracking test, these tests being conducted with utmost care. Strips of 1 mm. in thickness, 2 mm'. in width, and 200 mm. in length, made of many 'diflerent aluminum alloys were hardened by heating them up-to 450 C. and suddenly cooled in water After this, they were anealed at a temperature of C. for about light alloys widely of aluminum.

Pieces 1 and 2 in the above table represent the known as E alloy and Sanders alloy, respectively. Piece 3 is about the same in the range of 4 to 'l, but lacks the tent. Pieces4 to 7 are alloys the present invention.

' It is clear from the foregoing table that an addition of a, small percentage of chromium and calcium to the alloys imparts to them forgeability and p. remarkable resistance to season cracking. The light alloys of the present invention are therefore peculiarly well suited chromium and calcium conmade according to season cracking are essential, as in the case of materials for, aeroplane manufacturing. 7 e

In making the-alloys according to'this invention, three different mother alloys .consisting of aluminum and copper, of aluminum and manganese, and of aluminum and chromium are first prepared, and these three alloys are then melted consisting of 4-20% of zinc, 1-3% of cop of magnesium, 0.1- -1.5% of manganese, 0.05-.-1% of chromium, 0.01-0.2% of calcium. the rest IBAMUIIGARASHI. I GORO constituents and composition as Nos.

for use in many.

situations where high'tensile strength and nonaluminum, to which magnesium 5'0 1 what is claimed Aluminum alloys characterised by ready forge-. ability and resistance to season cracking1 

